DE60302188T2 - Apparatus and method for inkjet printing - Google Patents

Description

The The present invention relates to an ink jet printing apparatus and an ink jet printing method wherein an image is ejected by ejecting ink droplets formed from an ink jet print head with an array of nozzles becomes. In particular, the invention relates to an ink jet printing apparatus and an ink jet printing method wherein causes of print image quality deterioration analyzed and corrected, and thereby a high quality Print image is formed.

The Invention can be applied to all devices, the print media like paper, cloth, leather, fleece, OHP sheets and even use sheet metal. Examples of applicable facilities include an office equipment, such as Printers, photocopiers and facsimile machines, and industrial manufacturing facilities.

There information processing equipment such as copiers, word processing systems and computer and communication facilities are spreading more and more, Ink jet printing devices proliferate very much as a printing device to output digital images processed by these devices become. For a faster print speed use these printing devices a printhead with a large one Number of integrally formed nozzles, each of an ink ejection port and a liquid path consist. With the growing trend in recent years in Direction of color information processing equipment exists an increased Demands on printing devices for a color printability. To fulfill This requirement uses general inkjet printing devices a plurality of parallel printheads for ejecting ink droplets different colors.

The Inkjet printing device puffs droplets from Ink, a recording liquid, on a print medium, such as paper, to form dots on it. Since the ink jet printing apparatus makes the print head contactless to the Holding pressure medium, a low-noise printing operation can be performed. There Further, it is possible to increase the density of the ink ejection nozzles resolution to increase an image and the speed of printing cost-effective too increase. Another advantage of the inkjet printing device is that they have no special processing such as development and fixation requires, and high quality images on print media How can produce unprinted paper at low cost.

by virtue of Of these advantages, the inkjet printing device finds a wide Field of use. In particular, an ink jet printing apparatus Demand type will be more in demand in the future, since she can easily record a color printing technique and also downsized and can be simplified. The more printing devices color printing apply, the stronger is the trend towards higher picture quality and printing speed.

With the conventional printing devices described above however, the following problems are associated. Clogging at the usual Inkjet printing devices, the inkjet printheads respectively Use with a variety of lined up nozzles, one or more the nozzles, or can for some reason not as usual to be addressed, dots to be printed by these nozzles will not printed on a print medium. Non-printed sections appear in the form of ribbons (white bands or stripes) in an image, causing a noticeable deterioration the picture quality dependent on the degree of appearance of strip-like non-printed sections is caused. Falling as well one or more nozzles in an ejection state, that of other normal nozzles noticeably different, and will print in this state continued, sometimes white bands or stripes appear due of uneven densities in the picture, what the picture quality severely impaired.

In the case where some nozzles do not eject ink in a proper ejection state, it has been proposed to perform the following methods for alleviating image quality deterioration caused by failed or defective nozzles. The conventional methods that prioritize image quality include a method of restoring ink ejection performance using a cleaning method and a so-called multi-printing method that prints the same area of a print medium multiple times using a plurality of complementary nozzle groups to complete an image. However, the multi-printing method involves the problem that it takes a lot of time since a plurality of printing operations are performed every single printing area. The method of restoring ejection performance using, for example, a cleaning technique also requires a lot of time and consumes an additional amount of ink that does not contribute directly to printing. Because the process of restoring output increases the running costs and the environmental costs Viewpoint is not desired, the number of executions of the recovery operation should be kept to a minimum.

It Also, a technique was developed, called a head tint to the Preventing density fluctuations of a printed image and so on used to improve a print image quality. A general known head-tinting method involves printing a test pattern of uniform gray scale on a print medium, the optical detection of density fluctuations and the implementation of Corrections, such as addition or subtraction of gray scale values an output image when it is printed.

Of Further, in an ink jet printer with printheads, the each having a plurality of juxtaposed ink ejection nozzles, a test pattern with even gray scale value output and print density deviations (or pressure density fluctuations) are measured optically. It is believed that the pressure density fluctuations caused by fluctuations in the discharge amount among the nozzles become. There were efforts undertaken, the density or ejection quantity fluctuations among the Nozzles like by correcting an ink ejection driving method accordingly the density fluctuations or by performing a gamma correction of To improve gray scale in that part of a picture, that of the respective one Nozzle corresponds.

A Such a technique for correcting a density variation of a printed For example, picture is in Japanese Laid-Open Publication No. 3-33508 (1991), Japanese Patent Laid-Open No. 61-283273 (1986), 3-166959 (1991) and 7-242004 (1995). The effort described above for one Image Enhancement using the head tint but should fundamentally fluctuations in the amount of an ink droplet correct, which is ejected from a respective nozzle. For example, should the head tint not the picture quality to improve to an optimal level when one out of a faulty one Nozzle ejected ink droplets lands a position that is considerably far from an ideal position is removed, that is, has not landed at an ideal position. In particular, in a full multi-inkjet printing device, the full-line heads a so-called full-line printing system used with a a certain printhead connected image by the implementation only a scan of the printhead relative to a print medium finished there is a need for further image quality improvements.

To the Fulfill This requirement is also met by the inventor of this invention Ink jet printing device proposed. In this printing device be for each printhead takes measurements of deviations between actual Positions on a print media where ink droplets have landed those from individual nozzles pushed out are performed, and ideal landing positions on the pressure medium at those the ink droplets to land (pixel training positions on a print matrix). Then there are nozzles identifies a deviation of the ink droplets from the intended print matrix have caused. Image data corresponding to the identified nozzles and nearby image data will be used to eliminate the landing position deviations corrected.

This Procedure is very useful there always a satisfactory picture regardless of the presence of a variety of factors of ink ejection over the Flying up to landing can be made, the ink droplet landing position deviations can cause.

Of Furthermore arises with so-called extended printheads with over one Distance from above An inch of nozzles lined up a problem that the amount on image data to be processed becomes large when the nozzles with a high density of 360 dpi or more are arranged. For example with a printhead with nozzles, which at 600 dpi over an A4 size range (8 inches), the total number of nozzles reaches 4800. The implementation the above-described deviation correction processing all these jets requires processing a very large amount of data. This takes a long time Time during of printing, reflecting the overall working speed of the device slowed down. To eliminate this problem is a costly Processor required high-speed processing carry out can.

created Furthermore, a problem with a part of the nozzle column, must be conventional due to the presence of such a defective nozzle, the printhead as a low quality printhead be treated, which can lead to elimination of the printhead. In the case of extended printheads So in practice a big one Number of normally functioning nozzles wasted, which is a serious problem in terms of cost and ecology raises.

Of Further, such extended nozzles are as described above a greater probability that they nozzle ejection feature variations Experienced. For example, you can themselves nozzles with ink ejection amount fluctuations or those with landing position variations in a part of the nozzles in total focus. conventional become printheads all thrown away with errors as defective products. Indeed does not exist among the printheads treated as defective products few products whose ejection quantity fluctuations and landing position variations are low and only a few faulty nozzles exhibit. The use of these discarded products will reduce the manufacturing costs reduce the device and this realization is required.

The US 2001/0038397 A1 discloses an ink jet recording apparatus of the line scan type, which finely ejects ink from a respective nozzle and can control individually. The ink ejection control is performed such that an impact position of an ink droplet and an ink ejection amount at the same time for every Nozzle in addition to adapted to an adjustment of the ink ejection speed become. A difference between a measured impact position and a target landing position is calculated, and the difference becomes nozzle profile data added. Accordingly, an ejection position is changed so that Changed the impact position appropriately becomes.

Of Further, EP-A-0 694 396 discloses a recording apparatus to carry out a complementary one Record for removing the caused by recording elements white Stripes during recording an image that can no longer record.

Also describes WO 02/02329 A1 discloses an inkjet error tolerance using oversized drops become. To compensate an empty or matte line due to no ink or not enough Ink caused by a malfunctioning device Adjacent drops of ink are made larger than they are due to the raw image data would have to be.

The The present invention has been overcome the above disadvantages and provides an ink jet printing apparatus according to claim 1 and an ink jet printing method according to claim 16 ready at a printhead with a faulty nozzle, the ink droplets with a big one Deviation from an intended position ejects, undesirable visible bands or can prevent streaks in a printed image a picture of high quality be ensured with a suitable Graukalkalarstellung can.

In In this description, the word "nozzles" means a structure that is not just the openings contains, about the To eject ink is, but also cylindrical fluid paths or spaces that with the openings communicate and the ink and discharge energy production facilities (for example, electrothermal transducers, piezoelectric elements, etc.) for generating energy for ejecting the ink into the liquid path from the ejection openings take up.

There with the invention having the structure described above, the dot deviation correction Based on deviation data is carried out, the deviation amount or a Difference between an actual Landing position of a formed on the print medium by an ink droplet Ink dot ejected from a respective nozzle of the print head, and represent an ideal landing position of the ink dot, and because the deviation correcting means the dot deviation correction according to the deviation amount selectively To run can, even if the print head has a defective nozzle, their point landing position strongly from an intended position deviates, possible, a picture of high quality without visible bands or to produce stripes. Therefore, printheads with such faulty No nozzles can be replaced and over one long period of use.

This not only significantly reduces the running cost of the device, but is also ecological Viewpoint desirable. The invention can therefore practically the yield of printheads a Improve the production line and reduce the production costs of the print heads.

There the dot deviation correction by the deviation correcting means further only then executed may be required if the correction is based on the amount of deviation can be held for the minimizing the processing time required for the correction process, which ensures an efficient printing process.

The advantages of the invention described above are particularly significant in a printing system in which a single scan image of a printhead is arrayed with an array of nozzles is finished. The invention can also be applied to a so-called multi-pass printing in which one and the same printing area is scanned several times by different nozzle groups. Unwanted streaks or bands in a printed image that have already been reduced by the multi-pass printing can be further reduced by this invention. The invention is therefore applicable to any type of inkjet printing system.

The above and other objects, effects, features and advantages The invention will become apparent from the following description of the embodiments in conjunction with the accompanying drawings.

The above and other objects, effects, features and advantages The invention will become apparent from the following description of the embodiments in conjunction with the accompanying drawings.

1 Fig. 11 is a front view showing a layout of an ink jet printing apparatus according to an embodiment of the invention;

2 shows an enlarged schematic view of a structure of an ink jet print head A in 1 .

3 FIG. 12 is a block diagram of an example structure of a control system according to the embodiment of the invention; FIG.

4A shows an example staircase representation for identifying defective nozzles in a printhead formed by a printhead with normal nozzles;

4B shows an example staircase representation for identifying defective nozzles in a printhead formed by a printhead having defective nozzles at the 18th, 28th, and 30th positions;

5A FIG. 11 is an exemplary dot representation for identifying defective nozzles in a printhead formed by a printhead with normal nozzles; FIG.

5B FIG. 11 is an example point view for identifying defective nozzles in a printhead formed by a printhead having defective nozzles at the 18th, 28th, and 30th positions; FIG.

6 shows a plurality of shapes of ink dots formed on a print medium by ink droplets ejected from nozzles of a print head;

7A Figure 12 is a schematic representation of an ideal matrix used in the embodiment of the invention and of ink droplets that have landed on the ideal matrix on a print medium in an ideal manner;

7B Figure 12 is a schematic representation of an ideal matrix used in the embodiment of the invention and of ink droplets which have not landed ideally on the ideal matrix on a printing medium;

8th FIG. 12 is a flowchart showing an example control process according to a first embodiment of the invention; FIG.

9A Fig. 14 is an explanatory diagram showing how a plurality of ink dots formed by ink droplets ejected from nozzles influence one of ideal matrix lines according to the first embodiment, including a print head, an ideal matrix, ink droplets that have landed in an ideal manner, and ink droplets are shown who have not landed in an ideal way,

9B Fig. 12 is an explanatory diagram showing how a plurality of ink dots formed by ink droplets ejected from nozzles affect one of ideal matrix lines according to the first embodiment and an enlarged state of three rows of dots d (m-1), d (m); d (m + 1) in the center of the point group in 9A .

10 Fig. 12 is an explanatory view showing ink dots discharged through nozzles ejected from nozzles and an enlarged state of three rows of points d (m-1), d (m), d (m + 1) in the center of the point group in FIG 9A .

11A FIG. 12 is an explanatory view of a plurality of ink dots ejected from nozzles according to the first embodiment, which deviates from their intended positions; FIG.

11B FIG. 12 is an explanatory diagram of a method of calculating a degree at which a plurality of ink dots affect one of ideal matrix lines; FIG.

12 shows a flowchart of a control process according to a second embodiment of the invention,

13 shows a flowchart of a control process according to a third embodiment of the invention,

14 shows a flowchart of a control process according to a fourth embodiment of the invention,

15A shows an example staircase representation for identifying defective nozzles in a printhead formed by a printhead with normal nozzles;

15B shows an example staircase representation for identifying faulty nozzles in a printhead formed by a printhead having defective nozzles at the 18th, 28th, and 30th positions, and Figs

16 FIG. 12 is a flowchart of an example control process according to an embodiment of the invention. FIG.

below Be exemplary embodiments the invention with reference to the accompanying drawings described in more detail.

1 Fig. 12 shows a layout of an arrangement of an ink-jet printing apparatus used in embodiments of the invention. On a sledge 20 are a variety of inkjet printheads 21 ( 21-1 to 21-4 ) each having an array of nozzles or ink ejection openings. With 21-1 . 21-2 . 21-3 and 21-4 For example, each of ink-jet printheads (simply referred to as printheads) for ejecting black (K), cyan (C), magenta (M), and yellow (Y) ink is referred to. Inside (or liquid path) each ink nozzle of each printhead 21 a heating element (electrothermal transducer) is provided which generates thermal energy for ejecting ink. ink cartridges 22 each comprise an ink jet printhead 21-1 to 21-4 and an ink tank 22-1 to 22-4 ,

Control and other signals for the inkjet printheads 21 be via a flexible cable 23 Posted. A print medium 24 such as an OHP sheet, glossy paper, a glossy film and a postcard are on opposite feed rollers, not shown, to pairs of opposing discharge rollers 25 which hold the print medium and by a feed motor 26 for advancing in the arrow direction (sub-scanning direction) to be driven. The sled 20 becomes mobile on a guide shaft 27 and a linear encoder 28 carried. The sled 20 is powered by a carriage motor 30 via a belt drive 29 for reciprocating along the guide shaft 27 in the main scanning direction, which cuts (in this case, perpendicular) the sub scanning direction. Will the sled 20 is moved back and forth, one from the linear encoder 28 output pulse signal counted to the current position of the carriage 20 to determine. Will the sled 20 driven, the heat elements in the printheads become 21 energized according to the print signal for ejecting ink droplets onto a print medium to form an image.

At a starting position of the carriage 20 that is set outside a printing area via the printing medium in the main scanning direction is a restoration unit 32 with a cap section 31 Installed. If no printing is performed, the carriage will become 20 moves to the home position where ink ejection surfaces of the printheads 21 with associated caps 31-1 to 31-4 of the cap section 31 hermetically sealed to prevent possible clogging due to increased viscosity of the ink or solidified ink from ink solvent evaporation or sticking of a foreign material such as dust.

The covering function of the cap section 31 is also used for a free ejection of the nozzles for ejecting ink into the cap portion 31 causes no contact with the nozzles to prevent erroneous ejection and clogging such nozzles with low printing frequency. The capping function is also used for restoring the ejection performance of defective nozzles by activating a pump, not shown, for sucking ink from the nozzles, the ink ejection surfaces passing through the cap portion 31 hermetically covered. With 33 an ink receiving portion is designated. If every printhead 21-1 to 21-4 immediately before the beginning of a printing operation on the ink receiving portion 33 comes over, the printhead performs a preliminary ejection in the direction of the ink receiving portion 33 by. Further, a wiper member (not shown) (such as a sipe) is on the side of the cap portion 31 installed to the ink ejection surfaces of the printheads 21 to clean.

2 shows an enlarged schematic representation of the structure of the printheads described above 21 , According to 2 Each of the printheads has a large number of ink ejection nozzles n arranged in a direction nearly perpendicular to the main scanning direction. While in this figure the nozzles in each printhead are arranged in two columns, they may be arranged in one column or in three or more columns. They do not have to be arranged in a straight line. Further, as in 2 shown an interval W1 between adjacent nozzles in the sub-scanning direction called resolution of a print head or nozzle pitch or nozzle density.

The printheads can on a width W of the nozzle column corresponding area by ejecting Print ink when moving in the direction of the arrow (main scan direction). The printing process (ink ejecting operation) can be used in forward or reverse direction or both directions become. Furthermore, the printheads are provided in the same number, as there are ink colors for printing. For example, become three Colors, cyan, magenta and yellow used for full-color printing, are three printheads provided. Is monochromatic printing using just black ink, just a printhead to be provided. When printing using darker and lighter inks so many printheads like color inks like dark cyan, light cyan, dark magenta, light magenta, dark black, light black, dark yellow and be provided bright yellow. It is also possible to use a printhead for expel to use a particular color ink.

The The ink jet printing system applicable to this invention is not on bubble jet (trade name) systems using heating elements (Heaters) limited. For example, in a continuous type, the continuous ink droplets to atomization Charge control system and a dispersion control system can be used. Further, in the demand type which ejects ink droplets when needed Pressure control system can be used, the ink droplets from openings by mechanical Vibrations piezoelectric elements ejects.

3 Fig. 12 is a block diagram showing an example structure of a control system of an ink-jet printing apparatus used in embodiments of the invention.

In 3 denotes the reference numeral 1 an image data input unit for inputting multi-valued image data from an image input device such as a scanner and digital camera, and multi-valued image data stored on a hard disk of a personal computer, for example, 2 a control unit with various keys for setting a variety of parameters and for starting a printing operation and 3 a CPU as a control means for controlling various arithmetic operations and control actions, which are described below, and executed in accordance with programs in a storage medium.

With 4 is a storage medium called a control program group 4b with a control program for controlling the printing apparatus and an error processing program and nozzle profile information 4a stores. The printing operations in this embodiment are performed by these programs. The storage medium 4 storing these programs can use a ROM, an FD, a CD-ROM, an HD, a memory card, and a magneto-optical disk. 5 denotes a RAM that serves as a workspace for the programs on the storage medium 4 , is used as a temporary save area for error handling and as a work area for image processing. The RAM 5 can also be used in the following way. After copying various tables from the storage medium 4 in the RAM 5 For example, the contents of the tables can be changed and the image processing performed by referring to the modified tables.

The reference number 6 denotes an image data processing unit that quantizes the input multi-valued image data into N-value image data for each picture element and generates ejection pattern data based on a quantized gray scale value "T" on each picture element. For example, multi-valued image data represented by 8-bits (256 gray scales) is input to the image data input unit 1 entered, the image data processing unit must 6 convert the grayscale value of the image data to 25 (= 24 + 1) value data. Although the processing for transforming the input gray scale image data into T-value data uses a multi-valued error diffusion method, the T-value data generation processing may employ any desired halftoning processing such as an average density memory method and a dither matrix method. The repetition of the T-value data generation processing in accordance with the image density information for all picture elements may generate binary drive signals that cause individual nozzles to eject or not eject at each picture element. Noise information generation means, estimation means and correction information generation means are mainly executed by the image data processing unit 6 and the CPU 3 educated. Further, it is also possible to perform control by a printer driver used by a personal computer.

The reference number 7 denotes a printing unit that is an ink cartridge 22 and a sled 20 and ink corresponding to one through the image data processing unit 6 generated ejection pattern ejects to form a dot image on a printing medium. The reference number 8th denotes a bus line in the printing apparatus for transmitting address signals, data, control signals, etc.

With reference to the 4 to 11 For example, a process for generating nozzle information for printheads, which is one of features of this embodiment, an operation for generating printing information for each nozzle based on the nozzle information and an actual printing operation will be described.

at the generation of print information is checked if there are nozzles in printheads, whose ink landing positions deviate from a desired print matrix. Are such nozzles it is necessary to determine nozzle information, the positions of such nozzles, the extent, with the landing positions of ink droplets ejected from these nozzles differ from the print matrix and, depending on circumstances, sizes of landing ink droplets and forms of formed ink dots.

For this purpose, a as in 4 shown test pattern (step pattern or stair pattern) using a device according to 1 printed. The stair pattern consists of short printed line segments, eight segments of eight nozzles in each row formed by causing each nozzle to eject color dots continuously or not continuously over a short distance. This test pattern pressure is performed for a required number of nozzles. This stair pattern indicates how much the ink dots formed in the vertical direction in the figure deviate from the ideal print matrix MT. In particular, the printed test pattern (or step illustration) is scanned by a sensor, not shown, to measure how many microns the line segments deviate from their ideal landing positions. The measured deviations are used as nozzle profile information. Instead of using the sensor, it is also possible to visually determine deviating positions and the amount of deviation to generate nozzle profile information and to input this information into the printing device. This nozzle information is formed for each printhead.

Dot position deviations can be determined as follows. An ideal staircase is called Reference previously using a general printing method or a silver salt image. Then a test print of a Staircase display on the reference staircase for measuring of deviations from the ideal pressure matrix. alternative this may be the printed staircase representation of a not shown Scanner read and opposite the ideal pressure matrix under consideration the nozzle positions be checked for the calculation of deviations.

As another nozzle profile information generating method, it is also possible to use a dot representation as in FIG 5 to print, which consists of independent ink dots of individual nozzles formed on a printing medium, and by the method described above to read deviations from the ideal printing matrix in X and Y directions and in the diameter and shapes of ink dots.

An image-pressure signal can be generated by a method commonly used in a conventional ink-jet printing apparatus. In this embodiment, an input image is color-divided into images of three primary colors, such as C, M, and Y, which coincide with the ink colors of printheads vote. Then, the color separated images are binarized by an error diffusion method.

When next For example, a method for generating head correction (HC) data is based on a nozzle profile and a method for generating print data for controlling Ejection / non-ejection operations of Nozzles in printheads through execution a conversion processing in an image to be printed described.

7 shows a basic concept of this embodiment. This means, 7 illustrates an ideal print matrix MT and a state of ink dots that have ideally landed on the ideal print matrix MT. The ideal print matrix MT refers to a virtual matrix set on a print medium. When a solid image is formed by arranging ink dots of a certain shape in a matrix on a printing medium, minimum unit printing areas corresponding to individual dots 1: 1 are unit matrices MT1. The unit matrices are also called picture elements. For the sake of convenience, the ideal printing matrix MT of this embodiment comprises square unit arrays MT1 arranged in the main scanning direction (in the figure in the horizontal direction) and in the sub-scanning direction (in the figure in the vertical direction) as in FIG 7 are shown shown. Depending on a resolution of an image and a print density, the arrangement of the unit matrices MT1 may be different from the one in FIG 7 be shown different. The unit matrices MT1 may have shapes other than square. For example, rectangular unit arrays may be arranged in the main scanning direction at twice the height of the sub-scanning direction.

lands Ink on the ideal print matrix MT, land ink droplets a print medium usually as almost circular dots. It is therefore assumed that ink dots that have landed ideally have the shape of a perfect circle, and a diameter of one perfect circle becomes equal to a diagonal length of a unit matrix MT1 set.

A state of ideally landed ink dots is in 7A shown. The points shown schematically represent a state of a solid image printed by ejecting ink droplets from all eight nozzles arranged in the vertical direction in a print head, not shown, while moving the print head in the main scanning direction X. 7A shows a state of ink dots formed by ink droplets that ideally land on a print medium, and 7B Figure 12 shows a state of ink dots formed by ink droplets that do not land ideally on the print medium.

In the state in 7A For example, ink droplets ejected from the nozzles of the print head have landed correctly on the individual unit matrices MT1 in the ideal print matrix MT without deviation. Therefore, an array of dots in the vertical direction (Y) coincides with a vertical array of nozzles in the printhead. For example, third dots d3 from the top of the figure are dots ejected from a third nozzle from the top of the nozzle group of the print head; and fourth points d4 from above are dots ejected from a fourth nozzle from the top of the nozzle group.

In contrast, an example state of ink dots in 7B which are formed when ink droplets from the printhead do not land ideally on a print medium.

According to the figure are dots d2 formed by ink droplets that from a second nozzle pushed out from their ideal positions in the X1 and Y2 directions (upwards right). Dots d3 formed by ink droplets be from a third nozzle pushed out are shifted in the Y1 direction and almost land Unit matrices where ink droplets should be ejected from the fourth nozzle.

Further are dots d4 that are formed by ink droplets that from a fourth nozzle pushed out be moved in the Y2 direction and land on unit matrices, where from the third nozzle expelled ink droplets should land.

On Having a pressure medium formed by a sixth nozzle d6 points a larger diameter, because their quantities of ink are greater than those of other nozzles are.

Further have dots d7 made by ink droplets that from a seventh nozzle pushed out become smaller in diameter because their amounts of ink are lower than those of other jets, or there ejected ink droplets are split.

Although the ink dots in 7 are shown as faithful circles, they can not be formed as perfect circles, from ejection to landing, depending on the type of the printing medium and a state change of the ink. As in 6 As shown, ink dots assume a variety of shapes on a print medium that are different from perfect circles. For example, variations in ink ejection amount among nozzles result in variations in dot size, and since ink droplets landed on a print medium are absorbed and fixed on the paper surface, ink is drawn into the fibers of the paper, forming complex shapes of dots as shown become. If ink droplets do not land vertically on a print medium or are exposed to wind for a moment, the dots may become oval or broken into fragments.

That is, in a process from ink ejection from ink jet nozzles to spot landing on a print medium, the ink droplet landing position sometimes deviates from an ideal landing position. The ejected ink droplets may not fly in an intended direction or experience resistance to flying. Even after landing on a print medium, ink droplets are affected by an uneven surface of the print medium and its ability to suck and fix in the print medium. Because of these uncontrollable factors, the formation of points of perfectly uniform shape at suitable positions is difficult to achieve. That is, it is extremely difficult to get ideal points like in 7A shown to form.

Around to cope with this difficulty is conventional Practice to perform a correction processing such as a head tint. The Idea behind the conventional one head shading is following. Because positions on a print medium that through a Nozzle with a big one Ink discharge amount is printed, have a high density, and positions through a nozzle with low ink ejection amount printed, have a low density, becomes a representation printed at a predetermined density on a printing medium and actual Densities of the printed representation are measured and compared to the corresponding ones nozzle positions compared. Then, corrections for decreasing the density become Positions where the measured image density is higher than normal, and for increase the density is performed at positions where the measured image density less than normal. The density adjustment to improve the picture quality is achieved by modifying a drive control for each nozzle, that is, by shortening a drive pulse for nozzles, their ejection quantities are big, and increasing a drive voltage for nozzles, their ejection quantities are low.

In this head-tone correction, however, there are cases in which no correction can be made and desired effects are not obtained. For example, when ink droplets ejected from the third nozzle and the ink droplets ejected from the fourth nozzle intersect each other and as shown in FIG 7B shown, a desired effect can not be generated from the correction. That is, if the density of the third unit arrays is high, this problem is tracked as the improper ejection amount of the fourth nozzle. In this case, when the head-tinting processing is performed by comparing read image densities with nozzle positions and decreasing the ejection amount of the third nozzle as described above, it can be seen that the correction of the ejection amount does not work well for the correction of the image density variations because the ink dots ejected from the third nozzle d3 land on fourth unit matrices.

give way according to one another example point land positions from an ideal pressure matrix in X and Y directions, increase the differing points the density of an adjacent matrix line and reduce the density of an intended matrix line. In this Case results in the execution the conventional head tint one Correction that the density of the nozzle associated with the deviating increased adjacent row of lines, there the head tint not taken into account the landing position deviations. As a result, will the density of the adjacent matrix row further increases what an exact correction impossible power.

The invention is intended to eliminate the problems that could not be solved with the conventional method, and allow more precise corrections. In this invention, there is a situation in which the opposite correction is made as compared with the conventional method. For example, when correction data is supplied to a nozzle assigned to an N-th screen pressure, which is suitable when the ejection volume of this nozzle is small, this invention can correct for an image input signal to make it even smaller based on correction data calculated by estimation close. This will be described below. When nozzles adjacent to the N-th grid nozzle have deviations in the ink ejection direction, and dots formed by these adjacent nozzles overflow their own printing areas into the printing area of the Nth raster, the Nth raster image density may be caused by the overflowing portions of the adjacent raster dots increase influence. In this case, has the Nozzle printing the N-th screen has a small ejection volume, correction is made such that the density is further reduced to minimize visible streaks or density variations in a printed image. That is, while the conventional correction causes nozzles having a small ejection volume to perform a higher-density printing than an input image signal, the invention can perform a completely different correction from the conventional method. With this characteristic correction, the invention minimizes visible streaks or density variations.

the The problem of visible streaks or density variations has traditionally been by averaging great and low density values of adjacent matrix rows or by reading adjacent image areas in addition encountered reading a target image area. In the ink jet printing apparatus, from the present strongly demanded that it should fulfill an ever higher image quality, is a more precise correction technique required.

To meet this requirement, the first embodiment of the invention performs processing as shown in the flowchart in FIG 8th is shown.

First, in step S1, step diagrams as in FIG 4 as shown, so that the state of ink droplets from individual nozzles landed on a printing medium can be observed. Next, the printed charts are read by an optical sensor (not shown) (step S2), and based on the data thus read, deviations of the landing positions from an ideal print matrix are measured. This measurement can be performed visually. After printing the dot chart from 5 For example, the size and shape of dots landed on a printing medium can be measured using an optical sensor, not shown, to determine the ejection volume and the ejection amount of each ink droplet, respectively.

finds This measurement out that some points are not on the ideal Pressure matrix are that some points of an ideal point diameter have different diameters, or that some points from one ideal dot shape have different shapes, the nozzles, the These points have formed as faulty nozzles set. alternative to do this without a check up faulty nozzles possible, one Step to automatically generate nozzle profile information for all nozzles.

Become no faulty nozzles detects, the processing proceeds to step S6, where a desired Picture without execution a correction processing is printed.

Becomes in step S2, a faulty nozzle found, nozzle profile information described below for each of Generates nozzles, which consists of a printhead. In this embodiment, a Y deviation value becomes as an important parameter of the nozzle profile information used. A column direction of nozzles that make up the printhead is (a sub-scanning direction) be a Y direction, and a main scanning direction, in which the print head is moved relative to the print medium, let a X-direction. Then, the Y deviation value means a deviation amount in the Y direction between a landing position of an ink droplet ejected from a nozzle (Center position of a point) and a center position of the corresponding one Unit matrix (ideal grid point) of the ideal pressure matrix MT. It is thus assumed that when performing one-time sampling (1-pass) printing a nozzle width equal to the size of unit matrices the ideal landing matrix or set to 1200 dpi (around 20 μm) is. Dodges the landing position of an ink droplet ejected from an mth nozzle by half of a picture element in the direction of the (m-1) -th or (m + 1) -th nozzle, the Y deviation value is +10 μm or -10 μm, and this Value is called the nozzle profile information saved. At the same time, information about whether a diameter of this ink dot (which may be defined by the discharge volume is determined) greater than one ideal ink dot diameter is handled as the nozzle profile information.

With reference to 8th the process after step S2 will be described. As described above, the Y deviation amount of defective nozzles is measured in step S3, and based on the measured values, nozzle profile information is generated (step S3). Then HS data is generated by referring to the nozzle profile information (step S4). Based on the HS data, HC data (head correction table) corresponding to the size of input image print data is generated (step S5). Then, using the generated HC data, the print data of the input image is converted and a printing operation is performed according to the converted print data (step S6).

Hereinafter, generation of a variety of information performed in and after step S4 will be described in detail with reference to FIG 9 to 11 described.

9A shows schematically from left to right a print head 21 , an ideal print matrix MT, a state of ink dots that have ideally landed on the ideal print matrix MT, and a state of ink dots that have not landed ideally on the ideal print matrix MT. To simplify the description, the printhead is 21 shown with only five nozzles. 9B is an enlarged view of details of the middle three ink dot rows in the dot group in FIG 9A ,

The Data generation is accomplished by identifying such nozzles Ink dots ejected have at least part of a certain matrix line of the cover ideal pressure matrix MT, as determining nozzles, the affect a density of this matrix row, and by determining a percentage of this section of each ink dot of the determining nozzles carried out, which affects the density of this particular matrix row.

For example, consider a case where droplets of dots ejected from the (m-1) -th, m-th and (m + 1) -th nozzles are dots d (m-1), d (m), d (m + 1) form as it is in 9B is shown. How these points affect the density of an m-th matrix row is determined as follows. A portion of the ink dot d (m-1) formed by the (m-1) -th nozzle which is above the m-th matrix row and affects the density of that row (a hatched portion in a left nozzle column in FIG 9B ) is 10% of an ideal point. A portion of the ink dot d (m) ejected from the mth nozzle affecting the mth matrix row (in 9B a hatched section in a central nozzle column) is 80% of an ideal point. A portion of the ink dot d (m + 1) ejected from the (m + 1) -th nozzle affecting the m-th matrix row (in 9B a hatched section in a right-hand nozzle column) is 5% of an ideal point. This dot landing state is equal to 95% of an ideal dot landing state in terms of printed density.

While a particular row on the print matrix has been considered here, it is possible to have a percentage of an affecting portion of each adjacent dot for each target unit matrix MT1, as in FIG 10 shown to be determined.

Of the Percentage of points that determine the density of a given point Matrix line influence (degree of influence) can be by reference on nozzle profile information, Specifically, Y deviation values in the information are determined as follows become.

For example, it is assumed that a nozzle width (equivalent to the unit printing matrix size) is 20 μm (which corresponds to 1200 dpi) and that each nozzle forms an ink dot having a diameter of 30 μm on a printing medium. It is also assumed that a direction from a (m-1) -th row to an m-th row is assumed to be a positive direction, and that a Y-deviation value of a point from the (m-1) -th nozzle is +5 μm, a Y deviation value of a point from the m-th nozzle is +10 μm, and a Y deviation value of a point from the (m + 1) -th nozzle is -5 μm. As in 11A That is, the density of the m-th matrix row is determined from the following formulas based on the points of the (m-1) -th nozzle, the m-th nozzle, and the (m + 1) -th nozzle.

In 11B R is a dot radius, S is a dot area, Y is a Y deviation value, and P is a width of a print matrix line. Then, a percentage (degree of influence) of this portion of the point d (m-1) affecting the density of the m-th matrix row becomes Z _m-1 (L) (L is a number representing a matrix row position) follows determined: Z m-1 (L) = R 2 × cosθ -1 ((P / 2 - Y n-1 ) / R) - (P / 2 - Y n-1 ) × √ (R 2 + (P / 2 - Y n-1 ) 2 )

A degree of influence of this portion of the point d (m + 1) affecting the m-th matrix row, Z _{m + 1} (L), can also be determined in a similar manner.

Of the Center angle θ is an angle formed by two line segments (Radii), the one point center and two intersecting points between the Connect point and the mth matrix line.

Further, the degree of influence of this portion of the point d (m) affecting the m-th matrix row, Z _m (L) can be obtained from the following equation. Z m (L) = 100 - Z m (L - 1) - Z m (L + 1) (%)

If different nozzles have different dot radii, the degree of influence can be determined by inserting individual radius values are calculated.

is Furthermore, the dot shape of the circle, the degree of the Influence also in a similar way be determined, the calculation is complicated. In this Case can be a complex shape to a predetermined simple shape approximated which allows a simpler calculation.

By Analyze a printed state of a particular matrix line (L), especially of nozzles, which affect the density of this matrix line, the density estimated from the matrix row become.

That is, when D _{i represents} a density generated by an ideal printed dot, and D _{L represents} an estimated density of the line L, the estimated density D _{L is expressed} by the following equation expressing the degrees of influence Z (L) of the ( m - a) -th to (m + b) -th nozzles added (a and b are positive integers). D L = k the (Z ma (L) ... Z m-1 (L) + Z m (L) + Z m + 1 (L) ... Z m + b (L))

k is a coefficient _to which is determined for determining an actual density on the basis of a dot area, and can be calculated by measuring a density of a printed image.

A coefficient H _conf for the head correction is given as follows: H conf (L) = k head × D L / D i

This gives a measure like the printed matrix to an actual density of a print medium contributes.

k _head is a coefficient for fine-tuning a coefficient K, and varies depending on the printing medium used and the printing environment, and can be determined experimentally.

H _conf is used for correcting an image to be printed and controlling a driving signal for the ejecting operation of each nozzle to change an ejection volume during the head-coloring process.

As considered above the above embodiment when printing, if for other matrix lines thought ink dots overlapping on a subject of interest Matrix row land, an effect of the dots of other lines a density of the matrix line of interest when performing Printing corrections. Thus, even with a printhead with nozzles, the ink droplets with deviations in the Y direction, a satisfactory Correction effect can be achieved, thereby forming images of high quality become.

Although a nozzle correction coefficient for each matrix line L is calculated in the above embodiment, it is possible, _m influence degrees to a particular matrix line L of adjacent matrix rows, Z _m-1 (L), Z _m (L), Z _{+ 1} (L), in calculating a correction coefficient for a (m-1) -th nozzle printing on a matrix line L-1 adjacent to the matrix line L. That is, a coefficient H _nozz for _{head correction} is calculated as follows. In the processing for a matrix line L, a head correction is also performed on the (m-1) -th nozzle to be printed on the matrix line L-1. That is, corrections are made to the nozzles which affect the density of the matrix line L and / or to an image printed by these nozzles.

When a matrix line L printed by a nozzle m is influenced by ink dots formed by nozzles printing on matrix lines L-1, L, L + 1, the coefficient H _nozz for _{head correction} is given as follows: H nozz (L) = Z m (L - 1) × H conf (L - 1) + Z m (L) × H conf (L) + Z m (L + 1) × H conf (L + 1))

Even though not shown in the above equation, may be any one desired Coefficient can be applied as needed at each term. The above Equation means that the correction coefficient for the nozzle m, the on the matrix line L also prints an estimated print density correction for the matrix lines (in the above equation L-1 and L + 1), which are influenced by ink dots formed by the nozzle m become.

The is called, based on the extent with the out of the nozzle m ejected Ink dots affect matrix lines L-1 and L + 1, i.e., based on the conditions these matrix lines L - 1, L, L + 1, the head correction data is calculated.

With The method described above may be a matrix line correction even if ink dots are heavy on an imaginary matrix line in the direction of an adjacent matrix line, by correcting from image data for the nozzles, which influence the matrix line of interest, and / or by Correcting ejection volumes these nozzles will be realized. In this way can be a very good correction function be achieved.

[Second, third and fourth embodiment]

at the first embodiment becomes a Y deviation value each ink dot as an important parameter in the setting the nozzle profile information used. The invention may include other values in addition to the Y deviation value as parameter.

For example, in a second embodiment of the invention as in 12 shown a dot diameter in addition to the Y deviation value of a defective nozzle used as a parameter, as shown in step S13. Furthermore, in a third embodiment of the invention as in 13 4, an X deviation value in addition to the Y deviation value and dot diameter is used as a parameter, as shown in step S23.

Furthermore, in a fourth embodiment of the invention as in 14 shown a dot shape in addition to the Y deviation value, dot diameter and X deviation value used as a parameter, as shown in step S33.

Setting as many parameters as possible as described in the second to fourth embodiments can produce more accurate nozzle profile information, which in turn provides an image with excellent coloration and better insensitivity to banding compared to the first embodiment. In the 12 to 14 Steps S13, S23, S33 correspond to steps S1, S2 and S4 to S6 described in the first embodiment, except for the above-mentioned steps.

The The invention can be used without problems in an ink-jet printing apparatus which are used a variety of darker and lighter inks and size and small points for every ink color used. In this case, a greatly improved picture quality be generated on a print medium.

[Example 1]

When next For example, some examples of printing will be made using the inkjet printing device and the printing method according to the first embodiment of the invention.

One used printhead has a resolution of 1200 dpi and an array from 4096 nozzles, the ink ejection volume (Volume of each ink droplet) to 4.5 ± 0.5 pl is set.

colorants containing inks have the following compositions.

When Printing medium was PB PAPER (from Canon) for electrophotographic images and ink jet printing. Printing was done using this color inks and this printing medium performed.

A printing operation was performed according to one in the flowchart in FIG 8th controlled control sequence shown. First, a staircase diagram was made according to 4 output and then at a resolution of 4800 dpi read by an optical sensor (scanner), not shown. At this point, the diagram may be marked to match individual nozzles with their associated printed line segments with respect to their positional relationship. Then, each printed line segment was subjected to line thinning processing to determine a centroid of an ink dot and to measure a Y deviation value of the ink dot from its ideal landing position. This operation was performed on all nozzles for producing nozzle profiles.

Out Nozzle ejected ink dots had a landing precision of 6 μm as a σ value and a maximum deviation of +25 μm. Using this nozzle profile became a printed density for each matrix row is estimated from the formulas described above and Head correction data (HC data) has been generated. Then a density gray scale value became in print data of an image to be printed for each associated nozzle Corrected line. A variety of types of inks described above was used for printing. As a result, a high quality image with less Banding phenomenon and without white Received stripes.

in the Contrary to what has been described above, printing was by omission the head correction processing is performed, other conditions being similar to those maintained in the above example. This generated a picture of poor quality with visible white Stripes or ribbons.

The execution the conventional one Head shading processing when printing resulted in an image with reduced density variations but with persistent visible bands. An image quality deterioration is obviously, if a comparison with one by the above described example method generated image is performed.

Next, a fifth embodiment of the invention will be described. In this embodiment, the in the 1 to 3 shown construction as used in the previous embodiment.

Hereinafter, generation of printhead nozzle information, one of the features of this embodiment, generation of printing information for each nozzle based on the nozzle information, and an actual printing operation will be explained with reference mainly to FIGS 15 and 16 described.

to Generation of the printing information, the following operations must be performed. First, a check is made carried out, whether it is under the printhead nozzles a nozzle there, the ink droplets with deviations from an ideal pressure matrix. Gives it's such a nozzle, have to nozzle information be determined, the extent of the Deviation of one from this nozzle ejected ink droplet in terms of the pressure matrix and, if needed, a larger shape of one through the Nozzle formed Include ink dot.

To obtain the nozzle information, a first step to be performed is to print a stair pattern PT1 as shown in FIG 4 shown by a printing device off 1 is used. The stair pattern PT1 consists of short printed line segments, eight segments of eight nozzles in each row formed by causing each nozzle to eject color dots continuously or non-continuously over a short distance. This pattern printing is performed for a required number of nozzles. This stair pattern PT1 indicates how much distance the ink dots formed in the vertical direction in the figure deviate from the ideal print matrix MT. In particular, the printed staircase pattern (or step diagram) PT1 is scanned by a sensor, not shown, for measuring how many microns the line segments deviate from their ideal landing positions. The measured deviations are used as nozzle profile information. Instead of using the sensor, it is also possible to visually determine deviating positions and deviation amounts for generating nozzle profile information and to input this information into the printing device. The nozzle information is formed for each printhead.

Dot position deviations can be determined as follows. Before that becomes an ideal staircase diagram as a reference using a general printing method or a silver salt image. Then becomes a stair chart printed on the reference stair chart as a test to deviations to measure from the ideal pressure matrix. Alternatively, the printed staircase diagram by a scanning device, not shown read and with the ideal pressure matrix under consideration the nozzle positions be compared to calculate deviations.

The test pattern can be printed as solid state pattern from solid images. This solid state pattern only needs to have a uniform print density in a predetermined range. The solid state pattern may be, for example, a test pattern PT2 as in FIG 15 be shown. When the solid state pattern PT2 is completed by print-scanning (1-pass printing) using a print head with defective nozzles, stripes or bands are formed or density fluctuations become visible as shown in FIG 15B is shown. These fluctuations are read or observed by the sensor to generate the nozzle profile information.

Further, a dot chart may be formed by using all nozzles for ejecting ink to form independent ink dots on a print medium as in FIG 5 be caused to be shown. Using the method described above, deviations of these ink dots from the ideal print matrix in X and Y directions and diameter and shapes of the dots to produce the nozzle profile information are read.

Image printing signals can be generated by a method commonly used in conventional Ink jet devices is applied. In this embodiment An input image will be in three CMY primary colors for printheads of the corresponding colors color separated and then the color-separated images through an error diffusion process is binarized.

When next For example, a method for generating head correction (HC) data will be based on the nozzle profile and a method of implementation a conversion processing based on the HC data at a described image to be printed and for generating print data, the one ejection / non-ejection operation the respective printhead nozzles Taxes.

First a gray scale correction control will be described.

A position on a print medium printed by a nozzle having a large ink ejection volume (volume of the ink droplet) in an ejection process has a high density, while a position printed by a nozzle having a small ink ejection volume has a low density. A diagram (solid state diagram PT2 in 15 ) of a pattern having a uniform density is printed on a printing medium. The actual densities of printed positions are measured and compared with the nozzle positions for consistency. Corrections are made to reduce the density in portions of the printed image where the measured density is higher than normal and to increase the density in portions where the measured density is less than normal. This density adjustment for improving the image quality is achieved by a so-called head tint which modifies a drive for each nozzle for controlling the ink ejection volume, such as shortening a drive pulse for nozzles whose ejection volumes are large, and increasing a drive voltage for nozzles whose ejection volumes are small , and increases or decreases the print data at corresponding positions on an image to be printed. Simultaneously with the performance of the head tint, the ink droplet deviation correction described in the above embodiment is also performed to enhance the image quality. In the fifth embodiment of the invention, for example, a control according to the control sequence in FIG 16 carried out.

First, in step S1, a staircase diagram of a stair pattern PT1 and a fixed diagram of a fixed pattern PT2 are printed as shown in FIG 15 is shown. Then, a printed density of the solid chart is measured by an optical sensor, not shown, and based on measured density variations in the fixed chart PT2, fluctuations in the ink ejection volume among nozzles are determined and stored as head tone data (HC data) (step S2).

In step S2, the printed stair chart is read by an optical sensor, not shown, and based on the data thus read, deviations between dot land positions and an ideal print matrix are measured. This measurement can be performed visually. Further, the volumes of the ejected ink droplets are printed by printing a dot chart according to FIG 5 and measuring the sizes and shapes of dots landed on a printing medium, measured by an optical sensor, not shown.

If the measurement indicates that some ink dots are not positioned on the ideal print matrix, that their diameters are different from an ideal diameter, or that their shapes are different from an ideal one, those nozzles that ejected ink droplets to form those dots will be considered faulty nozzles determined. Alternatively, without performing the verification step For erroneous nozzles, proceed to a step of automatically generating nozzle profiles for almost all nozzles. Other nozzles that have not been determined to be defective are not subjected to the correction processing and are allowed to perform printing in accordance with the image data.

Gives there are faulty nozzles, become nozzle profile information for every the nozzles, which form the printhead, as described below. The is called, in this embodiment become the head tinting information (HS), which are obtained from the fixed diagram, and those from the Treppenarstellung obtained nozzle profile information generated.

To the generation of the nozzle profile information about the Measurement of the Y deviation values of the defective nozzles is checked step S4 the HS data and the nozzle profile data (NP data) on faulty nozzles.

The is called, the NP data is checked to see if it is a nozzle that gives such a large spot landing position error in terms of the ideal pressure matrix causing a predetermined pressure Value exceeds (in this case half a resolution). Such a nozzle is called "faulty Nozzle of large deviation ".

It There is also a case where the ejection volume fluctuation is large enough may be to cause a density fluctuation, though the spot land aberration is small, so the density of one formed by ejecting ink droplets Image of an appropriate density by an amount beyond a predetermined allowable Deviates from the area. For example, a density fluctuation through a specific nozzle while of 1-pass printing of a solid pattern, it becomes Nozzle simply as "faulty Nozzle "with real Printheads especially with those with an extended nozzle array can faulty nozzles with greater Deviation concentrate in one area, and nozzles with large ejection volume fluctuations in one other area. Although this rarely happens, the printhead can uneven nozzle diameter and molds, and nozzles can be deformed by loads. In conventional practice, a printhead with such nozzles identified as defective and completely thrown away. With this embodiment can but such printheads, which were previously treated as defective products, again for Use will be provided depending on how bad the printheads are. This embodiment can also be worn nozzles due to a long usage time or failed nozzles due to Dust penetration or faulty nozzles with large deviation serve.

kick a faulty nozzle with big ones Deviation to HC data (head correction table data) for those nozzles in the Near this faulty nozzle by a deviation correction control method as described below (Step S5) is generated. The HC data is generated with the HS data of HS data for integrated the entire print head. Using the generated HS data becomes one Grayscale correction on an output image signal for generation corrected print data performed (Step S6). A printing process will now be according to the corrected Print data executed (Step S7).

Become is found no erroneous nozzles of large deviation in the above step S4 the HC data generation is omitted in step S5 and a gray scale correction is used in image printing data through the use of HS data, the in step S2, that is, the original HS data is performed without considering the HC data.

at this embodiment As described above, the HC data generation is not performed for all nozzles, but only for those faulty nozzles, the size Cause dot position deviations. This embodiment therefore improves the data processing speed significantly compared with the configuration that generates the HC data for all nozzles. Because the faulty Nozzles of large deviation low compared to the total number of nozzles of a printhead in number and since this embodiment calculations are only for the very few nozzles executing, is the time for the generation of HC data is therefore minimal and has little adverse Effect on the overall printing process, which makes an effective Printing a picture with good quality is ensured.

While the invention is particularly effective in a 1-pass printing system, it can also be effectively applied to a so-called multi-pass printing system in which one and the same printing area is scanned several times by different groups of print head nozzles to complete an image in that area. In general multi-pass printing systems, after the detection of a defective nozzle, the area printed by this defective nozzle becomes other nozzles groups are printed during various scans to alleviate image quality degradation caused by the faulty nozzle. However, with the invention, the image quality deterioration by a defective nozzle can be prevented by a simple processing method in virtually the same scan. In conjunction with the advantage of the multi-pass printing system, the invention can therefore form images of even higher quality.

Further, the invention is particularly effective in an ink jet printing apparatus in which a plurality of nozzles are arranged in a direction nearly perpendicular to the print scanning direction such that an interval between adjacent nozzles capable of printing simultaneously on the same scan is almost equal to an interval of pixels of one image to be printed, as in 2 is shown, that is, in a full-line type ink jet printing apparatus that completes image printing in a single scan. The full-line type ink jet printing apparatus basically has the advantage in the multi-pass printing system of having a simpler structure and achieving a much higher printing speed. When the invention is applied to the full-line type system, it can improve the image quality and thus realize an ink jet printing apparatus having excellent performances in terms of cost, printing speed and image quality.

is the interval between adjacent nozzles is wider than the interval between adjacent print matrix lines, i.e., the resolution of the Printhead is lower than that of the print matrix, can be a nesting system be applied, in which the printing position of the printhead to a smaller distance than the nozzle interval to print dots between the already printed matrix lines is moved from points, or another printhead with higher resolution can used, the ink droplets of the same color. Even if another printhead used with different resolution In this case, printing can be done virtually the same way with respect to the pressure matrix, as if these printheads would print in the same scan. Therefore, this invention also be suitably applied to a nesting printing system.

Become but those jets, which can print in adjacent matrix lines, actually placed close to each other the inkjet printer can be built in a simpler way and Print faster as described above. Therefore, the invention especially for Full multi-type printer suitable.

adjacent Be nozzles preferably to the following resolution dependent on set for the purpose of image printing. For example, a Image of small size, like a so-called purse image with an inkjet printer with high quality are printed, adjacent nozzles are preferably at an interval of about 300 dpi (100 μm) set if their ink ejection volume is 40 ± 10 pl lies. Have the nozzles an ink ejection volume of about 10 ± 5 pl, they preferably become closer together at around 600 dpi (40 μm) placed. Further, the interval is set to 1200 dpi (20 μm) for an ink ejection volume of about 5 ± 2 pl and at 2400 dpi (10 μm) for a Ink ejection volume of about 2 ± 1 pl.

Different as a picture of small size, that from near being considered becomes a big one Image viewed from a distance, with nozzles larger ink ejection volume printed, which have a relatively wider distance from each other. In this case, the invention can also be suitably applied.

In addition to the printing device using a printhead, the ink by heat energy ejects, the is produced by means of electrothermal transducers, the invention Also applicable to a printing device with a print head, the Ejects ink through piezoelectric elements. That is, the invention can be incorporated can be applied to any type of inkjet printing device, the Ejects ink from nozzles.

[Example 2]

When next An example 2 of the ink jet printing apparatus will be described and the printing method of the fifth embodiment carried out the invention Printing process described.

One Printhead has 4096 nozzles as in Example 1 above with a resolution of 1200 dpi, with a single ink ejection volume (Volume of an ink droplet) to 4.5 ± 0.5 pl is set.

compositions the colorant inks are the same as in Example 1.

A printing process control was performed according to the sequence in the flowchart of FIG 16 carried out.

First, a staircase diagram was made according to 4 and the printed stair chart was measured by a not shown optical sensor (scanner) at a resolution of 4800 dpi. Individual line segments of the staircase diagram were subjected to line thinning processing for determining centroids of the ink dots and thus measuring Y deviation values of ink dots from ideal dot landing positions. At the same time, a fixed printed diagram for determining printed density fluctuations and according to the above-described method for generating HS data (density fluctuation correction data) was also read. Based on the Y deviation values, NP data (nozzle profile data) was generated for all nozzles.

Out Nozzle ejected ink dots had a landing precision of 6 μm in the σ value and a maximum deviation of +25 μm. A nozzle that forms an ink dot, its Y deviation value is half the nozzle spacing 1200 dpi (21.7 μm), i.e., 10.8 μm, exceeds is called a faulty nozzle greater Deviation treated. For Nozzles in nearby this faulty nozzle greater Deviation (for example, five Nozzles in front and after the faulty nozzle greater Deviation) were estimated printed densities using their NP data according to the Formulas for Generating HC Data (Dot Position Deviation Correction Data) described above calculated. The HC data (for those nozzles near the faulty nozzle with a Y deviation value over half the resolution) were for the HS data (density fluctuation correction data) for correcting a Density gray scale value in the print data of an image to be printed for every the one with the respective nozzles connected print matrix lines used. Printing processes were carried out using the above-mentioned types of inks. received printed images had image quality with reduced visible Stiffening without white Strips.

[Example 3]

at In this example, the criterion was whether a nozzle in question a faulty nozzle or not, to 25% of the resolution set, the other conditions being equal to those in Example 1 are. The number of erroneous nozzles of large deviation was 50%.

In In this case, a good image quality could be obtained, but doubled the data processing time is due to a doubled number of nozzles, which required a dot deviation correction control.

[Example 4]

at In this example, the criterion was whether a nozzle in question was one faulty nozzle or not, to 10% of the resolution set, the other conditions being equal to those in Example 1 were. The number of erroneous nozzles of large deviation was 80%.

Also in this case, a picture of good quality could be obtained, however the data processing time longer than in the previous examples, as the number of nozzles has increased, which required a dot deviation correction control.

[Example 5]

at In this example, the criterion was whether a nozzle in question was one faulty nozzle was or not, set to 100% of the resolution, with the conditions were the same as those in Example 1. The number faulty nozzles greater Deviation was 1%.

In In this case, the image obtained was of better quality than that with the conventional one Method, but the image quality improvement was not so noticeable as in example 1. However, the data processing time has become significant reduced compared to the previous examples.

The Invention achieves a clear effect when used in a recording head or a recording device that is a device for generating thermal energy, such as electrothermal Transducer or laser light, and the changes in the Ink by the heat energy for ejection causes the ink. The reason for this is that such a system is a high-density recording and high trigger can reach.

One typical structure and a typical operation of such Systems are disclosed in U.S. Patent Nos. 4,723,129 and 4,740,796, the use of this basic principle to implement of such a system is preferable.

The Invention has been detailed using preferred embodiments described, and it is for the Specialist can see that changes and modifications performed can be without departing from the claimed invention.

Claims (21)

An ink-jet printing apparatus that forms an image on a print medium by moving a print head having an array of nozzles and the print medium relative to each other with ejection of ink droplets from the nozzles in accordance with print data of the image to be printed, with nozzle information generating means for generating nozzle information ( 4a representing an ejection characteristic of a respective nozzle corresponding to a landing state of the ink droplet ejected from the respective nozzle on the printing medium, estimating means for estimating an effect based on the nozzle information generated by the nozzle information generating means and the printing data ejecting the ink droplets ejected from the respective nozzle the image to be formed, correction information generating means for generating correction information for correcting an ink ejection condition of each nozzle according to a result of the estimation by the estimating means and a control means (Fig. 3 ) for controlling a driving of the nozzles according to the print data and the correction information, the ink jet printing apparatus being characterized in that the estimating means is arranged at least for analyzing a component influencing a printing density on the printing medium, the component influencing the printing density passing through an ink dot of a certain one Nozzle and a printing area to be printed by an ink dot of a nozzle adjacent the particular nozzle, the adjacent nozzle overflowing from its own printing area into the printing area of the particular nozzle. An ink jet printing apparatus according to claim 1, characterized characterized in that the nozzle information generating means an extent of a Deviation between an ideal landing position of a respective landing position Nozzle of the Printhead ejected ink droplet on the print medium and an actual landing position of the ink droplet on the print medium as the nozzle information that determines the ejection property the respective nozzle represent. An ink jet printing apparatus according to claim 1 or 2, characterized in that the nozzle information generating means an ink ejection release / inhibition decision for every Nozzle of the Printhead and a size and / or Shape of an ink dot formed by each ink droplet, which lands on the print media as the nozzle information determines the the ejection property the respective nozzle represent. An ink jet printing apparatus according to any one of claims 1 to 3, characterized in that in a process for forming a Image the correction information generating device based on an estimated result from the estimator the correction information for correcting the ink ejection conditions of nozzles generated that are not capable of generating an ideal landing state. Ink jet printing apparatus according to claim 1, characterized by a deviation correcting means for performing a Point deviation correction based on deviation data representing an extent of a Deviation or difference between an actual Landing position of an ink dot by the one from a respective Nozzle ejected ink droplets the pressure medium is formed, and an ideal landing position of the Represent ink dot, wherein the control device for optional Causing the deviation correcting means to perform the dot deviation correction according to the extent of Deviation is set up. An ink jet printing apparatus according to claim 5, characterized by gray scale correcting means for performing ink dot gray scale correction in accordance with density difference data representing a density difference between an actual density of an ink dot formed on the printing medium and an ideal density of the dot the control means for controlling the gray scale correcting means and the deviation correcting means is arranged at least according to the density difference and the amount of deviation. An ink jet printing apparatus according to claim 5 or 6, characterized in that when the extent of the deviation of an ink dot of interest greater than a predetermined value the control means is the deviation correcting means for execution the point deviation correction causes. An ink jet printing apparatus according to claim 7, characterized characterized in that the deviation correcting means is an ink ejecting condition an influencing nozzle correct that the interesting ink spot when landing the ideal landing position adversely affected. An ink jet printing apparatus according to claim 7 or 8, characterized in that the influencing nozzle a Nozzle for expel an ink droplet for forming the ink dot of interest and / or adjacent ones Includes nozzles. An ink jet printing apparatus according to any one of claims 7 to 9, characterized in that when the extent of the deviation of the ink dot of interest exceeds 10% of a nozzle pitch, the control means the deviation correcting means for executing the Point deviation correction causes. An ink jet printing apparatus according to any one of claims 7 to 9, characterized in that when the extent of the deviation of the ink dot of interest exceeds 25% of a nozzle pitch, the control means the deviation correcting means for executing the Point deviation correction causes. An ink jet printing apparatus according to any one of claims 6 to 11, characterized in that the Grauskalakorrektureinrichtung based on the density data corresponding to an ink ejection condition of a nozzle corrected the density data. An ink jet printing apparatus according to any one of claims 5 to 12, characterized in that the deviation correcting means a volume of an ink droplet ejected from the influencing nozzle according to the extent of Deviation increased or decreased. An ink jet printing apparatus according to any one of claims 6 to 13, characterized in that the Grauskalakorrektureinrichtung a volume of one out of the nozzle expelled ink droplet according to a size of the density difference elevated or decreased. An ink jet printing apparatus according to any one of claims 6 to 14, characterized in that the control means the deviation correcting means and / or the gray scale correcting device according to nozzle information that controls an ejection feature a respective nozzle as an ink ejection enable / inhibit decision for the respective nozzle and a size and / or Shape of an ink dot. An ink-jet printing method that forms an image on a print medium by moving a print head having an array of nozzles and the print medium relative to each other with ejection of ink droplets from the nozzles according to print data of the image to be printed, with a nozzle information generation step (S3) for generating nozzle information representing an ejection characteristic of each nozzle according to a landing state of the ink droplet ejected from the respective nozzle on the print medium, an estimation step (S4) for estimating an effect based on the nozzle information generated by the nozzle information generating step and the print data that ejects the ink droplets ejected from each nozzle the image to be formed has, a correction information generating step (S5) for generating correction information for correcting an ink ejection condition of each nozzle according to a result the estimation by the estimation step, and a control step (S6) for controlling a driving of the nozzles according to the print data and the correction information, wherein the ink jet printing method is characterized in that the estimating step analyzes at least one component influencing a print density on the print medium wherein the component affecting the printing density comprises a printing area to be printed by an ink dot of a certain nozzle and a printing area to be printed by an ink dot of a nozzle adjacent to the particular nozzle, the adjacent nozzle overflowing from its own printing area to the printing area of the particular nozzle , An ink jet printing method according to claim 16, characterized characterized in that the nozzle information generating step a degree of deviation between an ideal landing position of a respective nozzle of the printhead expelled ink droplet on the print medium and an actual landing position of the ink droplet on the print medium as the nozzle information that determines the ejection property the respective nozzle represent. An ink jet printing method according to claim 16 or 17, characterized in that the nozzle information generating step an ink ejection release / inhibition decision for every Nozzle of the Printhead and a size and / or Shape of an ink dot formed by the respective ink droplet which lands on the print medium is determined as the nozzle information, the the ejection property the respective nozzle represent. An ink jet printing method according to any one of claims 16 to 18, characterized in that in a process of forming a Image of the correction information generating step based on a estimated Result from the estimation step the correction information for correcting the ink ejection conditions of nozzles generated that are not capable of generating an ideal landing state. Ink jet printing method according to claim 16, characterized by a deviation correcting step for performing a Point offset correction based on deviation data that is an extent of a Deviation or difference between an actual Landing position of one on the print medium by the one from a respective Nozzle ejected ink droplets formed Ink dot and an ideal landing position of the ink dot, and a control step for selectively causing the offset correcting step for execution the dot deviation correction according to the amount of the deviation. Ink jet printing method according to claim 20, characterized by a grayscale correction step for performing a Ink dot gray scale correction according to density difference data, which has a density difference between an actual density of one on the Printing medium formed ink dot and an ideal density of Point, and a control step for controlling the Grayscale correcting device and the deviation correcting device at least according to the density difference and the extent of the deviation.